SEOUL
— THE death of Kim Il Sung, for 46 years the Communist dictator of North Korea, came just as he seemed poised to bring his country in from the cold.

In the past few weeks the aging autocrat, the object of one of the most pervasive personality cults in modern times, appeared ready to end his country's long isolation.

After Kim's meeting with former President Carter last month, there was reason to believe that the international standoff over his country's alleged nuclear-weapons program might be resolved through negotiation instead of confrontation. Kim had agreed to meet his South Korean counterpart President Kim Young Sam on July 25, an event that promised significant progress toward the unification of two countries bitterly divided by the cold war.

But skeptics have always insisted that the North Korean dictator was not to be trusted. They warned that he was just playing for time, and that what seemed like concessions were really gambits designed to fool the West.

Suddenly Kim is gone and the optimism that had begun to take root in Seoul, Tokyo, and Washington has once again turned to uncertainty.

The disappointment is particularly acute in the South Korean capital. President Kim walked out of a luncheon meeting when he was informed of his northern counterpart's death. Analysts here say he had good reason to be upset, since the planned summit seemed to be an opportunity for a diplomatic breakthrough.

Now the question is: what next? The official announcement of Kim's death, released by North Korean authorities on Saturday, indicated that his son and heir-designate, Kim Jong Il, would indeed take over. Yesterday the official Korean Central News Agency (KCNA) broadcast words of praise for the younger Kim from senior government and military figures, quelling suspicions that a power struggle might be taking place in the North. Those doubts arose immediately, since the moderate steps the elder Kim took during Mr. Carter's visit were thought to be controversial among hard-line communists.

One observer in Seoul, a former South Korean government official who would not speak for attribution wondered yesterday why Kim Jong Il had not yet been seen in public. ``In our society, in any other society,'' the former official says, ``he would be seen paying tribute to his father. But nothing of this is coming through.'' Adding to the mystery was the northern announcement that the planned funeral service, set for July 17, would be closed to foreign visitors.

Also puzzling, the former official says, was the KCNA's release of a detailed explanation of the cause of Kim's death. Koreans rarely conduct post-mortem examinations, because of a belief in the uncleanliness of the dead. ``That communique, depending on how you look at it, suggests they must have felt a need to explain why they did the autopsy,'' he adds. ``It's a little self-conscious,'' he concludes, as if the North Koreans were trying too hard to convince the world that Kim Il Sung had died a natural death.

Although Kim Il Sung assiduously, and sometimes brutally, rid North Korea of any dissent during his reign, analysts argue that the North's government has become factionalized in recent years. A hard-line group, which some speculate is led by Kim Jong Il, is thought to be behind the alleged nuclear-weapons program. This faction may have found what Kim promised Carter - a freeze in the nuclear program, a resumption of dialogue with the US, and an offer to meet the South Korean leader - untenable.

UT equally baffling are reports in the South Korean press citing an anonymous Hong Kong source who claims to be in touch with North Korean officials who say that the North wants to pursue the planned summit. This tidbit of information - and tidbits are the coin of the realm in analyzing North Korea - suggests that Kim died of natural causes and that the momentum for moderation and opening may not be lost.

That analysis certainly represents the hope of many people here. Kil Jeong Woo, of the Research Institute for National Unification, argues that ``there are no other options for Kim Jong Il.''

The North's isolation has put the country on the verge of economic collapse, according to reports from northern defectors, and opening the country to international aid and trade is probably the only way to forestall that end. Furthermore, Dr. Kil and other experts say, the younger Kim lacks the charisma and standing his father had, and is therefore less able to force his people to accept deprivation.

``He will follow his father's gestures in relation to Washington,'' Kil concludes. He says the US, Japanese, and South Korean governments, more than ever before, must show the new North Korean regime what it has to gain by opening the country.

But no one here has a firm grasp on what kind of leader Kim Jong Il is likely to be. Although he was named to lead the country's armed forces in 1990, he strikes observers as reclusive and occasionally bizarre. Foreign visitors have seldom been granted interviews with him, and at various times in his life he seems to have concentrated mainly on cinema and architecture.

In South Korea, says Cho Se Hyung, a leading opposition member of the National Assembly, ``there are two schools of thought about Kim Jong Il.''

One school argues that Kim ``is unpredictable and very inferior to his father''; the other says ``He has been quite reasonable and is a member of a more moderate group,'' Mr. Cho notes.

Complicating the picture is that Kim Il Sung's North Korea is much more of a fiefdom rather than a political system. In a 1988 political biography called ``Kim Il Sung: The North Korean Leader,'' University of Hawaii professor Suh Dae Sook writes that ``what [Kim Il Sung] has built in the past four decades resembles more his personal kingdom than a Communist state, and the people he rules are more his loyal subjects than New Communists.''

Although the dynastic transition from father to son seems to be proceeding, the lack of any real knowledge about Kim Jong Il means anything is possible.